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1

Constraint Logic Programming with Polynomial Constraints over Finite Domains

Bergenti F., Monica S., Rossi G.

Fundamenta Informaticae

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2018

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Vol. 161, nr 1/2

9--27

EN

This paper introduces an instantiation of the constraint logic programming scheme called CLP(PolyFD) in which variables take values from finite subsets of the integers and constraints are expressed as equalities, inequalities, and disequalities of polynomials with integer coefficients. Such constraints, which we call polynomial constraints over finite domains, can be treated effectively by means of a specific solver under the assumption that initial approximations of the domains of variables are available. The proposed solver deals with constraints in a canonical form and it uses the modified Bernstein form of polynomials to detect the satisfiability of constraints. The solver is complete and a preliminary assessment of its performance is reported.

2

Nondeterministic Programming in Java with JSetL

Rossi G., Bergenti F.

Fundamenta Informaticae

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2015

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Vol. 140, nr 3/4

393--412

EN

JSetL is a Java library that endows Java with a number of facilities that are intended to support declarative and constraint (logic) programming. In this paper we show how JSetL can be used to support general forms of nondeterministic programming in an object-oriented framework. This is obtained by combining different but related facilities, such as logical variables, set data structures, unification, along with a constraint solver that allows the user to solve nondeterministic constraints as well as to define new constraints using the nondeterminism handling facilities provided by the solver itself. Thus, the user can define her/his own general nondeterministic procedures as new constraints, letting the constraint solver handle them. The proposed solutions are illustrated through a number of concrete Java programs using JSetL, including the implementation of simple Definite Clause Grammars.

3

Integrating Finite Domain and Set Constraints into a Set-based Constraint Language

Bergenti F., Dal Palu A., Rossi G.

Fundamenta Informaticae

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2009

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Vol. 96, nr 3

227-252

EN

This paper summarizes a constraint solving technique that is used to reason effectively in the scope of a set-based constraint language that supersedes existing finite domain languages. The first part of this paper motivates the presented work and introduces the constraint language, namely the language of Hereditarily Finite Sets (HFS). Then, the proposed constraint solver is detailed in terms of a set of rewrite rules that exploit finite domain reasoning within the HFS language. The proposed solution improves previous work on CLP(SET ) [11] by integrating intervals into the constraint system and by providing a new layered architecture for the solver that supports more effective constraint solving strategies. On the other hand, the proposed approach provides enhanced expressivity and flexibility of domain representation than those usually found in existing finite domain constraint solvers.